Here is the full list of all 19 Planetary Annihilation achievements.
Target an incoming planet with an annihilaser
Discover a new loadout in galactic war
Smash five enemy planets
Watch competitive play for eight hours as a spectator
Participate in ten team games
Watch competitive play for two hours as a spectator
Start a game with a custom system
Destroy five enemy planets with annihilasers
Annihilate your opposition throughout the galaxy
Activate an annihilaser
Kill a commander within five minutes, five times
Eliminate a faction in galactic war
Build every kind of unit
Build every structure in a single game
Build every kind of basic factory
Keep tabs on your conquest with ten camera anchors
Manage your armies with all ten control groups
Use more than 95% of the metal and energy you produce in a match
Win against three times as many players